Does the underwater treadmill really modify the way dogs walk?

Canine hydrotherapy is rapidly increasing in popularity as a way of helping dogs to recover from injury, managing degenerative musculoskeletal disorders and improving fitness. Some owners also take their dogs for hydrotherapy sessions to promote weight loss or in some cases just for fun.

Whilst the term canine hydrotherapy usually conjures up images of dogs swimming, underwater treadmills are also being increasingly used to provide a controlled environment for dogs to walk in water. The underwater treadmill has a number of advantages, including the ability to alter water depth and treadmill speed in order to better customise the session to meet the needs of individual animals.

Hydrotherapists often use visual observation to monitor improvement in movement after dogs have undergone a number of sessions on the underwater treadmill, but the question remains as to whether there is a more scientific way to assess these improvements. Sessions can be expensive and some animals may need to undergo therapy for a prolonged period, therefore, it is important that we can evidence the benefit of this therapy for dogs and gain data on the best protocols to use. This has already occurred for horses walking in water, but research on dogs is lacking compared to their equine counterparts.

A study by Monk and colleagues in 2006 found that underwater treadmill exercise resulted in increased range of movement of the stifle joint and increased muscle size compared to normal walking exercise. This particular research was specific to dogs recovering from a surgical procedure and the measurements were recorded quite soon after surgery. To build on from this study, fully understanding the long term benefits would be beneficial as well as ensuring the treatment plans are done purely on hydrotherapy and not using a multi-modal treatment plan. This way the exact benefit of the underwater treadmill can be determined and compared to physiotherapy and other exercise regimes.

In a recent study by Barnicoat and Wills published in 2016, the way dogs walk on an underwater treadmill was assessed for the first time in healthy dogs. Dogs walked at different depths and their limb movements were recorded using a motion capture system. The results indicated that dogs move very differently in water to how they walk on a dry treadmill. As the depth of water increased, dogs decreased the time within a stride that their foot was in contact with the ground, and spent more time swinging their leg. Dogs also took longer, more infrequent strides as the water became deeper, which may explain why dogs have an increased range of movement after a hydrotherapy session as seen by Monk and colleagues. This finding was also in keeping with what has been observed in horses, as a similar trend was observed by Scott and colleagues in 2010. This is an interesting observation as whilst superficially dogs might be considered similar to horses as they are athletic, four-legged animals, their movement on dry land does somewhat differ. These findings have an interesting application for sporting dogs, particularly where a longer stride length might result in increased performance. Hudson and colleagues in 2012 demonstrated how stride length increases speed in racing greyhounds, and these findings may also have relevance to agility dogs where the success of a round is determined by speed as well as the ability to clear fences.

In conclusion, from the studies undertaken we have learnt that hydrotherapy has seen positive results in both rehabilitation and performance and we can build from these studies further and understand in greater detail how dogs move in water. Dogs are the most diverse species in existence and therefore understanding how they move is a challenging task. We are also yet to compare whether other breeds may adapt their gait differently to underwater walking. A further point of interest is how long any potential changes to the way the dog moves, persist after the hydrotherapy session is completed. This information would enable hydrotherapists to design regimens more effectively and provide a more evidence based method of assessing the progress of patients.